In celebration of Netflix's live-action adaptation of the anime, I will be ranking most of the many story arcs (fillers included). These are just based on my personal opinion. So, here are arcs 35-31. Also, like with my Fairy Tail rankings, if there are any secondary paragraphs, those will be more spoiler-filled, though there aren't any here.
35. Ice Hunter
A filler arc before the Thriller Bark saga that follows a family of bounty hunters tracking the Straw Hat crew in the middle of a glacier. While not the worst of the fillers, it definitely ranks near the bottom. The villains were all 2-dimensional and boring as were most of the fights. The only saving grace was the final battle between Luffy and Don Accino as the villain's Hot-Hot fruit abilities prove to be a good match. It was also pretty funny to see the crew scrambling to recover their Jolly Roger since that was one thing Luffy would get mad about as captain. The Phoenix pirates also proved a nice touch as survivors of the second half of the Grand Line, their captain having given up hope. But ultimately, the antagonists were too weak to be taken seriously and were dragged out too long, like with most filler arcs. What could have been entertaining just turned into a slog for the most part.
34. Z's Ambition
Another filler arc, this one being the prologue for One Piece Film: Z as well as the introduction of the Straw Hats to the second half of the Grand Line. Overall, this arc was pretty enjoyable with Lily being an interesting new character, asking the crew to rescue her giant father. It also brought in Vice Admiral Momonga, one of the better Marines and a character with far too little screen time, for a short but sweet fight with Zoro. If this hadn't been all set up for the film and Momonga been the real antagonist, this arc would have been much better off. Instead, Shuzo and the Neo Marines served in that regard and while the action was fun, the outcome was always expected. Still, the killer move of Lily stretching Luffy from the inside into a giant was pretty awesome. And, just like all the other movie prologues, it is completely unnecessary to the film and is more than easily skippable.
33. Warship Island
The anime's first official filler arc (outside Buggy's adventures) that takes place right after Loguetown. Here, the Straw Hats find a young girl Apis floating in the sea and soon embark on an adventure to save a legendary dragon while keeping it hidden from the approaching Marines. Like the other filler arcs, this story doesn't offer much but it was a fun ride and did include the essential scene of the Calm Belt, explaining why people don't just sail into the Grand Line from the sides. It also has some funny Luffy accidentally hurting Zoro moments and the epic scene of Luffy cutting a battleship in half. But besides that, it's an arc that is unessential though still fun and honestly worth a watch.
32. Ocean's Dream Another filler arc but this is one that is actually pretty good. The crew all go to sleep near a mysterious island except for Robin. The next morning, they've all lost their memories of their travels together, leaving Robin, the most recent member, to try and figure out what's happening. However, without their memories, Nami goes back to hating pirates and Zoro returns to his old wanderer lifestyle. Seeing the crew forced into their own lives and then work together without knowing one another was really cool and this is one filler arc that I thought was too short as I would have watched more episodes eagerly. While the villain was a little on the lame side, he did grant us another Luffy v. Zoro fight even if it didn't last long and was an actual threat at the end. Goes to show how great and loyal the Straw Hats are as a team even when they don't know one another.
The Reverie is actually really important to the future of One Piece, containing many key plot points that set up the final act of the series, and the only non-filler arc featured in this list. The problem is, most of those plot points occur or are revealed in the Wano and Egghead arcs that come after. The Reverie arc itself is mostly a recap following the princesses Vivi, Shirahoshi, and Rebecca as well as various other figures. While it is really cool to see these characters interact with one another, there really isn't that much else to it. Still, Oda manages once again here to show why every detail of the story is important with the return of forgotten character Saint Donquixote Mjosgard from the Fishman Island arc flashback, something very unexpected but very welcome. Sadly, beside that, the Reverie arc doesn't offer much.
And that's the first five. Hope you enjoyed it so far and check back next week for the next batch of rankings.